Back in the 1950s when folks were still doing a lot of sporterizing on Mauser 98s, it was generally accepted that 1943 was the last year of reliability.
(My father tells of guys who would gather up a few hundred 98s and take a torch to the barrel and a saw to the stock; then they went into boxes for shipping back to the States. Hey, they were worth around $20 apiece!)
Original 98 or no, $500 seems around $200 too high, even in today's world...
Art